You can see a chronological overview of changes in each event on the Main tab - Activity Log button in the top right corner. You must of course grant the users permissions via Settings - Account - Users for them to view the Activity Log.
You can see here which user has changed something, and when. Not all types of changes are shown here, it mainly concerns important fields from Main such as:
Event name
Start date
Start Production
Doors open
Program start
End time
Venue
Space
Status
Project lead
Project type